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ORIGINAL ARTICLE
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Malignant peripheral nerve sheath tumor with analysis of various prognostic factors: A single-institutional experience


1 Department of Surgical Oncology, The Gujarat Cancer and Research Institute, Ahmedabad, Gujarat, India
2 Department of Oncopathology, The Gujarat Cancer and Research Institute, Ahmedabad, Gujarat, India
3 Department of Radiotherapy, The Gujarat Cancer and Research Institute, Ahmedabad, Gujarat, India

Date of Submission12-Oct-2019
Date of Decision25-Nov-2019
Date of Acceptance27-Jan-2020
Date of Web Publication22-Oct-2020

Correspondence Address:
Ketul Sureshbhai Puj,
Department of Surgical Oncology, The Gujarat Cancer and Research Institute, Civil Hospital Campus, Asarwa, Ahmedabad - 380 016, Gujarat
India
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/jcrt.JCRT_854_19

 > Abstract 


Context: Malignant peripheral nerve sheath tumor (MPNST) is a rare and aggressive soft-tissue sarcoma.
Aims: The aim of this study was to analyze various prognostic factors and treatment outcome of patients with MPNST.
Settings and Design: This was a retrospective study.
Subjects and Methods: Ninety-two patients, who presented with MPNST at a tertiary care cancer center from 2011 to 2018, were included in this study. The median follow-up of all living patients was 33 months. Neurofibromatosis 1 (NF1) was seen in 12 (13%) patients. Sixty (65.2%) patients received curative-intent treatment.
Statistical Analysis Used: Kaplan–Meier method was used for survival analysis. Log-rank test was used for univariate analysis, and multivariate analysis was done by Cox proportional hazard ratio method.
Results: The 5-year overall survival (OS) of all patients was 47.2% and the 5-year disease-free survival (DFS) of operated patients was 41.5%. On univariate analysis, association with NF1 (P = 0.009), grade (P = 0.017), and margin status (P = 0.002) had a significant effect on DFS, whereas association with NF1 (P = 0.025), metastatic disease on presentation (P < 0.0001), palliative intent of treatment (P < 0.0001), grade (P = 0.049), and margin status (P = 0.036) had a significant effect on OS. On multivariate analysis for patients who were treated with curative-intent treatment, grade (P = 0.015), and margin status (P = 0.028) had a significant effect on DFS, whereas association with NF1 (P = 0.00026) and location of tumor (P = 0.040) had a significant effect on OS.
Conclusions: The presence of distant metastasis, palliative intent of treatment, association with NF1, location of the tumor in the head and neck, high tumor grade, and positive margin status were the risk factors associated with poor survival for the patients with MPNST. Wide local excision with negative resection margin is the highly recommended treatment.

Keywords: Malignant peripheral nerve sheath tumor, neurofibromatosis 1, soft-tissue sarcoma



How to cite this URL:
Sharma MR, Puj KS, Salunke AA, Pandya SJ, Gandhi JS, Parikh AR. Malignant peripheral nerve sheath tumor with analysis of various prognostic factors: A single-institutional experience. J Can Res Ther [Epub ahead of print] [cited 2020 Dec 3]. Available from: https://www.cancerjournal.net/preprintarticle.asp?id=298868




 > Introduction Top


Malignant peripheral nerve sheath tumor (MPNST) is a soft-tissue sarcoma of neural origin. MPNSTs comprise approximately 5%–10% of all soft-tissue sarcomas.[1] Multiple terms were used historically for malignant nerve tumors, i.e., malignant schwannoma, neurofibrosarcoma, and neurogenic sarcoma have been replaced by MPNST.[1] They can arise from preexisting neurofibromas or de novo from peripheral nerves, but they rarely arise from schwannomas.[2],[3] They usually demonstrate Schwann cell differentiation on histological examination. MPNSTs can also occur as secondary neoplasms 10–20 years after radiotherapy (RT), accounting for up to 10% of MPNSTs.[4] 22%–50% of MPNSTs occur in patients with neurofibromatosis 1 (NF1) and the remaining lesions are sporadic.[5] In a patient with NF1, the risk of developing an MPNST is between 8% and 13%.[5] Most of them arise from preexisting plexiform neurofibromas. The median age for sporadic MPNST is between 30 and 60 years and that for NF1 associated MPNST is between 20 and 40 years.[6]

MPNSTs are commonly found on the extremities and trunk and less commonly on the head-and-neck region.[7] Most MPNSTs occur in conjunction with large peripheral nerves such as sciatic nerve, brachial plexus, and sacral plexus, but the nerve of origin is often not evident. The clinical features of MPNST are pain, rapid increase in size of tumor, and progressive neurological deficit, especially when occurring in a preexisting neurofibroma. Change in tumor size (T size) is most predictive of malignancy.[8] Due to the rarity of the disease, there are very few case series in the literature. In the present study, we analyzed various clinicopathological factors, treatment, and their impact on prognosis of the patients with MPNST at our institute.


 > Subjects and Methods Top


Ninety-two patients, who presented with MPNST from 2011 to 2018, were included in this retrospective longitudinal study conducted at a tertiary care cancer center. We reviewed the clinical records for follow-up of patients. We found that a total of 132 patients were diagnosed with MPNST (with primary or recurrent presentation) during this period, out of which we excluded 40 patients from our study who left to follow-up with follow-up period <6 months or whose data were grossly missing. The diagnosis of MPNST was confirmed by histological examination of tissue biopsy and immunohistochemistry. Slides were reviewed by our pathology department for all patients who came with outside histological diagnosis. All patients underwent local imaging in the form of magnetic resonance imaging for extremity, vertebral, and head-and-neck lesions; contrast-enhanced computed tomography (CECT) thorax for thoracic lesions; and CECT abdomen and pelvis for abdominopelvic mass; metastatic workup was done in the form of CECT thorax for all patients. Patients received multidisciplinary treatment in the form of surgery, radiation therapy, chemotherapy, and palliative therapy as indicated and decided by a multidisciplinary team. T size was determined according to the T stage of the American Joint Committee on Cancer eighth edition.[9] Margin status was defined by the following criteria: R0 = microscopically negative margins, R1 = microscopically positive, and R2 = macroscopically positive margins.

Follow-up surveillance was done by history and physical examination, local part imaging as indicated, and CECT thorax every 3–6 months for the first 2 years, then 6 monthly for next 2 years, and annually thereafter. Various factors such as age, sex, presence of NF1, location of tumor, recurrent presentation, metastatic disease on presentation, intent of treatment, grade, size, margin, and adjuvant RT were analyzed, and their impact on disease-free survival (DFS) and overall survival (OS) was studied. OS was counted from the date of histological diagnosis, and DFS was counted from the date of surgery. IBM SPSS Statistics for Windows, version 25 (IBM Corp, Armonk, NY) was used for statistical analysis. Kaplan–Meier method was used for survival analysis. Log-rank test was used for univariate analysis, and multivariate analysis was done by Cox proportional hazard ratio. Descriptive statistics was used for calculating median and interquartile range (IQR). P < 0·05 was considered as statistically significant.


 > Results Top


The median follow-up of all living patients was 33 months (IQR = 14–55 months). The median age of the patients was 41·50 years (IQR = 32–55 years). Demographic-, tumor-, and treatment-related characteristics were analyzed [Table 1].
Table 1: Demographic, tumor, and treatment characteristics of the malignant peripheral nerve sheath tumor cohort (n=92)

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Histologically, most MPNSTs showed densely cellular areas alternating with less cellular areas. The cells ranged from spindle to fusiform shaped. The nuclei were wavy, buckled, or comma shaped, and cytoplasm was lightly stained and indistinct. The French Fédération Nationale des Centres de Lutte Contre le Cancer (FNCLCC) grading was used to grade (Grade 1–3) the tumor. FNCLCC grade is determined by adding the score of three parameters: differentiation, mitotic activity, and extent of necrosis[1] [Figure 1]a, [Figure 1]b, [Figure 1]c. Epitheloid or other heterogeneous components (rhabdomyomatous, osseous, cartilaginous, liposarcomatous, glandular, or smooth muscle) can be observed occasionally in MPNSTs.[10] MPNST with rhabdomyomatous differentiation is called malignant triton tumor which is associated with a high grade of tumor and poor survival.[11],[12] In the current series, 8.7% (8/92) MPNSTs showed heterogeneous components. The most common was epitheloid differentiation (7/8), followed by rhabdomyomatous differentiation (2/8) and osseous differentiation (1/8). In one case, all three heterogeneous components mentioned above were present. All these MPNSTs with heterogeneous components were high grade (Grade 2 or 3) in the present study. On immunohistochemistry, S100 positivity was seen in 77.9% (60/77) cases (90% [54/60] focally positive and 10% [6/60] diffuse positive) [Figure 1]d, vimentin was positive in all cases, desmin was negative in 98.5% (65/66) cases, and actin was focally positive in 24.6% (15/61) cases. R0 resection was possible in 58.3% (35/60) patients. Out of 22 patients who presented with resection done outside our center, in two patients, reresection was performed and histologically negative (R0) margin was achieved. Majority of the patients (74% [68/92]) were having T size of more than 5 cm. Extremity was the most common location (57.6%, 53/92), followed by trunk (35.9%, 33/92) and head and neck (6.5%, 6/92), respectively. Thirty-two patients received palliative-intent treatment either due to metastatic disease, inoperable disease, or poor general condition. Out of 60 patients who received curative-intent treatment, seven patients (11.66%) underwent amputation for the removal of tumor. The rest of the patients underwent wide local excision. Thirty-two patients received adjuvant RT after wide local excision. Out of these 32 patients, 30 patients received postoperative external beam RT (EBRT), with assistance of radiopaque clips, which were placed in the tumor bed at the time of surgery. The total dose of 50 Gy in 20–25 fractions (200–250 cGy per fraction) was given. Five fractions per week were given over 4–5 weeks on cobalt or linear accelerator by three-dimensional conformal radiation therapy or electron beam after proper immobilization. The radiation margin was kept 5 cm craniocaudally to the tumor bed and surgical scar, whereas the radial margin was defined by the compartment and surgical bed. Among these, two patients also received adjuvant chemotherapy with RT (one patient received three cycles of doxorubicin plus ifosfamide before RT and one received four cycles of doxorubicin plus ifosfamide after completion of RT). Out of 32 patients, two patients received high-dose-rate (HDR) brachytherapy (18 Gy in six fractions and 3 Gy per fraction, two fractions per day, delivered over 3 days, through iridium-HDR microselectron) after 5–7 days of surgery by afterloading catheters. These catheters were placed intraoperatively after resection of tumor and were transversely placed in a single plane using a “grid” approach or in multiple planes with 2–3 cm margin around tumor bed, keeping a distance of 1.5–2 cm from vital structures and 1 cm from the next catheter. EBRT (40 Gy in 20 fractions) was also given after a gap of 7–14 days postbrachytherapy (for adequate wound healing) to these patients. No patients received preoperative RT treatment in the present study.
Figure 1: Histological findings (high-power view [×400]) of malignant peripheral nerve sheath tumor. (a) Grade 1 malignant peripheral nerve sheath tumor – spindle cells arranged in fascicles, (b) Grade 2 malignant peripheral nerve sheath tumor – spindle cells with intermediate nuclear features without necrosis, (c) Grade 3 – pleomorphic spindle cells, mitotic figures, and necrosis, (d) focal S100 positivity of malignant peripheral nerve sheath tumor

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Out of 60 patients who received curative treatment, 33 patients were disease free till their last follow-up. Twenty-seven patients (45%) developed disease recurrence or second primary tumor. Out of these 27 patients, 16 patients had only local recurrence, 1 patient had both local and nodal recurrences, 3 patients had only distal recurrence (distal metastasis), 5 patients had both local and distal recurrences, 1 patient had local recurrence with second primary, and 1 had second primary only. Out of these 27 patients, 6 patients were salvaged by curative treatment and the rest of the patients received palliative treatment. Out of these six salvaged patients, three patients were salvaged by wide local excision of their local recurrence, one by wide local excision and nodal dissection for locoregional recurrence, one by chemotherapy followed by radiofrequency ablation (RFA) of lung metastases, and one by chemotherapy followed by wide local excision of local recurrence and metastasectomy of lung metastases. All salvaged patients were alive at their last follow-up, and only one patient who operated for lung metastasectomy had recurrence of lung metastasis. The median follow-up of salvaged patients was 66 months (IQR = 36.25–79.25 months).

Out of 92 patients, 23 patients had documented distal metastasis, 15 on presentation, and 8 during follow-up after curative treatment. Sixteen patients had a single site and seven patients had multiple sites of metastasis. The sites of metastasis in decreasing frequency were lung (22, 95·7%), bone (3, 13%), nonregional nodes (3, 13%), and liver (2, 8·7%). Only two patients had regional nodal spread: one on presentation and another during follow-up, both of which were treated with nodal dissection.

Survival analysis

The 5-year OS of all patients was 47·2% and the median OS was 54 months. The 5-year DFS of operated patients was 41·5% and the median DFS was 21 months.

On univariate analysis [Table 2], association with NF1 (P = 0.009), grade (P = 0.017), and margin status (P = 0.002) had a significant effect on DFS, whereas higher T size (P = 0.090) and location in the head and neck (P = 0.069) showed trend toward decreased DFS. Association with NF1 (P = 0.025), metastatic disease on presentation (P < 0.0001), palliative intent of treatment (P < 0.0001), grade of tumor (P = 0.049), and margin status (P = 0.036) had a significant effect on OS, whereas factors such as age >45 years (P = 0.075), higher T size (P = 0.083), and location in the head and neck (P = 0.155) showed trend toward decreased OS.
Table 2: Univariate analysis of various factors for disease-free survival and overall survival

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Multivariate analysis [Table 3] was done for both OS and DFS, using variables (which have shown significant or trend toward a significant effect) for patients who received curative-intent treatment. Association with NF1 (P = 0.00026) and location of tumor (P = 0.04) had a significant effect on OS, whereas tumor grade (P = 0.015) and margin status (P = 0.028) had a significant effect on DFS.
Table 3: Multivariate analysis for patients who received curative treatment

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 > Discussion Top


MPNSTs are aggressive soft-tissue sarcomas with a 5-year OS ranging between 34 and 64%.[13],[14],[15],[16],[17],[18],[19] MPNSTs should be managed by the center experienced in the management of soft-tissue sarcomas with the involvement of a multidisciplinary team. The 5-year OS of all patients was 47·2% in the current study.

According to literature, 22%–50% of MPNSTs occur in patients with NF1;[5] in the present study, NF1 stigmata were present in 12 patients (13%), whereas 80 patients had sporadic MPNST. Patients with NF1 were younger than sporadic MPNST patients, which corresponds to the literature.[6] The median age was 28 years (IQR = 20.25–46.5 years) for patients with NF1 and 44.50 years (IQR = 32.25–55 years) for patients with sporadic MPNST. Median T size was 9.6 cm (IQR = 6.45–16 cm) for sporadic MPNST and 14 cm (IQR = 9.5–17 cm) for patients with NF1. All patients with NF1 presented with T2 or higher size. Fifty percent (6/12) of the NF1 patients were only amenable to receive curative treatment. DFS and OS were significantly lower in NF1-associated MPNSTs [Figure 2]a and [Figure 2]b. On multivariate analysis, NF1 significantly affected OS (P = 0.00026) but not DFS (P = 0.079). Probable reasons for low survival in NF1 patients appear to be larger T size, later presentation (as patients neglect the tumor considering it as neurofibroma) and development of second primary in NF1 patients. Porter et al. and Wong et al. also found poor survival in patients with NF1-associated MPNST.[20],[21] A recent meta-analysis by Kolberg et al. had shown no significant survival difference between sporadic- and NF1-associated MPNSTs.[22]
Figure 2: Kaplan–Meier survival curve showing (a) disease-free survival and (b) overall survival according to neurofibromatosis 1 status, (c) disease-free survival and (d) overall survival according to location of tumor, (e) overall survival according to intent of treatment and (f) overall survival according to metastatic disease on presentation

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Recurrent tumor presentation did not show any significant effect on DFS or OS in the current study. In contrary to our results, Goertz et al. found that recurrent tumor had poor DFS and OS.[18] Anghileri et al. also found poor outcome for patients who presented with recurrent tumor.[13]

The most common location of MPNST was extremity followed by trunk and head and neck, respectively [Table 1]. On univariate analysis for DFS, location in the extremity had favorable DFS, followed by trunk and head and neck, respectively, having trend toward decreased DFS. A probable reason is that lesions in the head and neck and trunk are more close to vital structures, which makes it difficult to achieve good resection margin. On univariate analysis for OS, location in the extremity and trunk had comparable survival, whereas location in the head neck had poor survival [Figure 2]c and [Figure 2]d. On multivariate analysis, location in the head and neck was significantly (P = 0.04) associated with decreased OS. On further analysis of extremity location, 34 (64.15%) patients had proximal limb lesions and 19 (35.85%) had distal limb involvement. Forty patients (75.47%) had lower limb involvement and 13 (24.53%) had upper limb involvement. However, on subanalysis, no significant difference of survival was seen between upper or lower limb (5-year OS, 56.5% vs. 45.5% respectively, P = 0.324) and proximal or distal limb involvement (5-year OS, 52.8% vs. 47.7%, respectively, P = 0.381). Anghileri et al., in their study, found that MPNSTs of the extremities had more favorable outcomes compared with MPNSTs of the trunk and of the head and neck.[13] Owosho et al. in their study of head-and-neck sarcomas found worst OS of MPNST as compared to other head-and-neck sarcomas.[23]

In the present series, patients treated with palliative intent due to metastatic disease, inoperable disease, or poor general condition had significantly poor OS (P < 0.0001) [Figure 2]e and [Figure 2]f. All patients with pulmonary metastasis on presentation were inoperable in this series, two patients who developed lung metastasis during follow-up underwent salvage procedure and were alive till date, which suggests that, whenever feasible, lung metastasis should be resected or to be targeted with other modalities such as RFA or stereotactic body radiation therapy. Literature also suggests that selected patients could benefit from a resection of pulmonary metastasis.[24]

The positive margin of resection was significantly associated with poor OS and DFS on univariate analysis [Figure 3]a and [Figure 3]b]. On multivariate analysis, it significantly affected DFS (P = 0.028) but not OS. Anghileri et al. and Wong et al. also reported a significant effect of margin status on survival, especially on DFS.[13],[21] Bernthal et al. determined that surgical margins did not have a significant effect on the clinical outcome of patients with low-grade MPNST; hence, obtaining wide resections with negative surgical margins in low-grade MPNST is not as critical compared with high-grade MPNST.[25] In the present series, positive margin rates according to the regions were as follows: extremity (22·6%, 7/31), head and neck (33.3%, 1/4), and trunk (33.3%, 4/12). Wong et al. reported a more positive margin in trunk lesions followed by head and neck and extremity, respectively.[21] About 11.66% of the patients underwent amputation for R0 resection in our series. Goertz et al. also reported an amputation rate of 11%.[18] Whenever possible, wide local excision with R0 resection should be the goal of treatment.
Figure 3: Kaplan–Meier survival curve showing (a) disease-free survival and (b) overall survival according to margin status, (c) disease-free survival and (d)-overall survival according to T size, (e) disease-free survival and (f) overall survival according to tumor grade

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Higher T size of the tumor showed a trend toward lower OS and DFS on univariate analysis [Figure 3]c and [Figure 3]d and nonsignificant impact on multivariate analysis [Table 3]. Various studies had shown that a larger T size is associated with poor survival.[13],[15],[19],[21]

Higher grade of the tumor was associated with lower DFS and OS on univariate analysis [Figure 3]e and [Figure 3]f. It also showed a significant effect on DFS on multivariate analysis (P = 0.015). On analysis of substrata, Grade 2 and Grade 3 tumors did not show a significant difference in DFS (P = 0.186) and OS (P = 0.768) between each other, which suggests that Grade 2 and Grade 3 tumors should be treated in the same line. Stucky et al. and Wong et al. also found poor survival with high tumor grade.[19],[21]

In the present study, though adjuvant RT showed improvement in OS and DFS, it was not statistically significant [Table 2]. A probable explanation of this may be due to the small sample size of our study and still long follow-up may be required to get its actual advantage. It is very premature to say no effect of postoperative RT by the analysis of this study. Various studies had shown a survival advantage with adjuvant RT.[4],[17],[21] Adjuvant RT is indicated for positive or close margins, size more than 5 cm, high grade of tumor, possible surgical field contamination, and recurrent tumors.[19]

The limitation of the current study is its retrospective nature. Second, the number of patients included in the current study is limited due to the rarity of this tumor.


 > Conclusions Top


MPNST should be treated in the institute experienced with the management of soft-tissue sarcoma with involvement of the multidisciplinary team. The most common location of MPNST was extremity followed by trunk and head and neck, respectively. The presence of distant metastasis, palliative intent of tumor, association with NF1, location of the tumor in the head and neck, high tumor grade, and positive margin status were the risk factors associated with poor survival for the patients with MPNST. Wide local excision with R0 resection margin is the highly recommended treatment. We suggest a multicentric study in the future for better analysis of various prognostic factors for this tumor.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
 > References Top

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Weiss S, Goldblum J. Malignant tumors of the peripheral nerves. In: Strauss M, Grey L, editors. Enzinger and Weiss's Soft Tissue Tumors. 4th ed. St. Louis: Mosby, Inc.; 2001. p. 1209-64.  Back to cited text no. 1
    
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McMenamin ME, Fletcher CD. Expanding the spectrum of malignant change in schwannomas: Epitheloid malignant change, Epitheloid malignant peripheral nerve sheath tumor, and Epitheloid angiosarcoma: A study of 17 cases. Am J Surg Pathol 2001;25:13-25.  Back to cited text no. 3
    
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Cashen DV, Parisien RC, Raskin K, Hornicek FJ, Gebhardt MC, Mankin HJ. Survival data for patients with malignant schwannoma. Clin Orthop Relat Res 2004;426:69-73.  Back to cited text no. 14
    
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Carli M, Ferrari A, Mattke A, Zanetti I, Casanova M, Bisogno G, et al. Pediatric malignant peripheral nerve sheath tumor: The Italian and German soft tissue sarcoma cooperative group. J Clin Oncol 2005;23:8422-30.  Back to cited text no. 17
    
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Goertz O, Langer S, Uthoff D, Ring A, Stricker I, Tannapfel A, et al. Diagnosis, treatment and survival of 65 patients with malignant peripheral nerve sheath tumors. Anticancer Res 2014;34:777-83.  Back to cited text no. 18
    
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Stucky CC, Johnson KN, Gray RJ, Pockaj BA, Ocal IT, Rose PS, et al. Malignant peripheral nerve sheath tumors (MPNST): The Mayo Clinic experience. Ann Surg Oncol 2012;19:878-85.  Back to cited text no. 19
    
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Porter DE, Prasad V, Foster L, Dall GF, Birch R, Grimer RJ. Survival in malignant peripheral nerve sheath tumours: A comparison between sporadic and neurofibromatosis type 1-associated tumours. Sarcoma 2009;2009:756395.  Back to cited text no. 20
    
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Kolberg M, Høland M, Agesen TH, Brekke HR, Liestøl K, Hall KS, et al. Survival meta-analyses for>1800 malignant peripheral nerve sheath tumor patients with and without neurofibromatosis type 1. Neuro Oncol 2013;15:135-47.  Back to cited text no. 22
    
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